An electric fan usually includes a set of blades having a curved configuration each. The set of blades is driven by a driving motor to rotate, so that air is sucked into the fan from one side of the blades and then blown out of the fan from the other side of the blades to thereby produce airflow toward a target object. However, the blades can only produce linearly moved airflow. To direct the linearly moved airflow produced by the fan to different directions, an oscillating mechanism must be additionally provided for the fan.
According to the oscillating mechanisms thereof, the currently available fans can be generally divided into two types, namely, a cover-rotating fan and an oscillating fan.
The cover-rotating fan includes an air guiding mechanism arranged at a front side of the overall fan structure. The air guiding mechanism normally includes a plurality of parallelly spaced tilted slats. When the air guiding mechanism is rotated, the originally linearly moved airflow produced by the fan meets the rotating tilted slats and is automatically directed to different flowing directions to thereby produce a widened breezy area.
To achieve the purpose of directing the airflow to different directions, the tilted slats of the air guiding mechanism for the fan are usually densely arranged. Dust tends to accumulate in the small spaces between the densely arranged tilted slats, and the densely arranged tilted slats would adversely restrict the range of airflow to result in lowered cooling efficiency. Therefore, such air guiding mechanism is not suitable for use with a fan system designed to produce a large airflow.
The oscillating fan is a fan provided in a base thereof with a rotary mechanism for producing an oscillating motion of the fan. That is, the rotary mechanism reciprocatingly rotates a main shaft of the fan to thereby change the direction of the produced airflow. When the oscillating fan operates, the whole fan oscillates about the rotary mechanism to swing to and fro sidewardly within a large span.
However, the sideward oscillation of the fan within a large span does not guide the airflow upward and downward. Therefore, the sideward oscillating fan is not suitable for some special working environment that requires vertical airflow. Further, the rotary mechanism of the oscillating fan has a gear set that is subject to wearing due to unbalanced weight undertaken by the rotary mechanism. The worn-out gear set results in a fan that tends to jig or halt during oscillating and accordingly has reduced operating efficiency and shortened service life.
On the other hand, most of the current industrial fans have metal-made blades and a powerful driving motor for rotating the blades at high speed, so as to meet the requirement of producing a large amount of airflow. The conventional oscillating fan and cover-rotating fan have a structure that fails to meet the requirement of the industrial fans. For the purpose of directing the airflow produced by the general industrial fan to different directions, the industrial fan is normally manually oriented to different directions. When orienting the industrial fan to different directions with a hand, there is a potential risk in the safety of using the industrial fan because the operator's hand might touch and be injured by the metal blades of the fan. Therefore, the conventional industrial fans have relatively low applicability.
In conclusion, the conventional fans, no matter what type of rotary mechanism is adopted, have the disadvantage of limited airflow direction or non-adjustable airflow direction. To overcome the above disadvantage, there is a developed fan structure for leading airflow to upper and lower sides of the fan. For example, US Patent Publication No. 2008/0304969 discloses a built-in swing mechanism of rotary fan. Please refer to FIG. 1. According to the specification of US Patent Publication No. 2008/0304969, the rotary fan has a main casing 10, a built-in swing mechanism 11 located in a main casing 10 of the rotary fan, and a fan driving motor 12. The built-in swing mechanism 11 includes a ball-and-socket support mechanism 13 arranged onto a front wall 101 of the main casing 10, and a crank oscillating mechanism 14 assembled to a rear wall 107 of the main casing 10.
The ball-and-socket support mechanism 13 includes a ball-and-socket support frame 102 arranged onto the front wall 101 of the main casing 10 and a spherical abut seat 106 having a spherical abut surface 105. The ball-and-socket support frame 102 has a spherical supporting surface 103 and a through-hole 104 located at a center of the spherical supporting surface 103 for a spindle 121 of the fan driving motor 12 to extend therethrough. The spherical abut seat 106 has an end coupled with the spherical supporting surface 103 via the spherical abut surface 105, and another opposing end connected to a front end of the fan driving motor 12.
The crank oscillating mechanism 14 includes a crank linkage element 141 assembled between the fan driving motor 12 and the rear wall 107 of the main casing 10. The crank linkage element 141 has a first end that can be driven to enable the oscillation of an opposing second end thereof. The second end of the crank linkage element 141 is assembled to a rotary pivot 142 on the rear wall 107 of the main casing 10 to rotate freely. The first end of the crank linkage element 141 includes a drive plate 146 and an independent motor gearbox 144 having an output shaft 143. The drive plate 146 is provided with an axle hole 145 for the output shaft 143 of the independent motor gearbox 144 to extend therethrough. The independent motor gearbox 144 is connected to a rear end of the fan driving motor 12.
When the built-in swing mechanism 11 of rotary fan operates, the independent motor gearbox 144 drives the crank oscillating mechanism 14 for the latter to bring the fan driving motor 12 to oscillate 360 degrees about the ball-and-socket support mechanism 13 at the front end of the main casing 10, so that the rotary fan can produce and deliver a 360-degree airflow.
However, as a most common problem with this type of rotary fan, the gearbox and the ball-and-socket support mechanism of the swing mechanism are subject to wearing due to unbalanced weight distribution over the swing mechanism. The worn-out gearbox and ball-and-socket support mechanism result in a fan that tends to jig or halt during oscillating and accordingly has reduced operating efficiency and shortened service life.